This invention relates generally to a floor structure for truck trailers, truck bodies, railway cars, and the like, and more particularly, but not by way of limitation, to a floor structure that combines both the benefits of high structural strength and enhanced air circulation.
Trucks, trailers, containers and railway cars utilized in the transportation of goods that require conditioned air, either heated or cooled, are constructed of an insulated enclosed compartment which is equipped with a mechanical unit that can supply heated or cooled air to this compartment. The distribution of this conditioned air about the cargo is of prime concern in maintaining the proper temperature for the goods while in transit. The conditioned air should be circulated over the top, around the sides and underneath the cargo. The cargo may rest directly on the floor, thereby preventing air circulation beneath the cargo unless the floor structure provides some means of air passage from front to rear.
One known floor structure is a corrugated extruded floor, commonly referred to as a "duct" floor. This floor type includes interconnecting panels made from extruded metals such as aluminum. The extrusions on these panels are a plurality of elongated, inverted U-shaped channels, equally and parallel-spaced. Spaces formed between the inverted U-shaped channels provide passage for air, and thus, circulate air along the floor. The amount of air passage is restricted by the size of the inverted U-shaped channels. the legs of the inverted U-shaped channels provide support for a horizontal, load-bearing surface that is connected to the upper edges of these supporting legs. This combination of the flat load-bearing surface and the supporting legs provides a high structural strength loading platform that can withstand high stresses such as can be imposed by forklift trucks or other means used to load cargo onto the floor. Since most cargos are loaded with some type of mechanical lift truck, the structural integrity of the floor is of prime importance. An example of a floor structure composed of duct panels is disclosed in U.S. Pat. No. 2,786,556 to Constance, Jr.
Another known type of floor structure is the "T-floor". This type of floor provides enhanced air circulation as well as a load-bearing surface. To obtain a greater amount of air passage space beneath the cargo this type of floor utilizes interconnected extruded metallic panels including a flat base from which a plurality of T-shaped members extend upward, with a horizontal flat area on which the cargo rests. A typical spacing between the T-shaped members provides a greater area for air circulation than in a typical duct panel. Examples of patents disclosing floor structures composed of T-panels are U.S. Pat. No. 3,368,315 to Thurnau; U.S. Pat. No. 2,923,384 to Black; and U.S. Pat. No. 2,952,341 to Weiler.
Although providing enhanced air circulation, the T-floors are relatively weak compared to duct floors. The design of T-floors, comprised of T-shaped members, with a single vertical leg supporting the horizontal surface and spaced apart with no connection between the horizontal surfaces can be damaged, collapsed or distorted by heavy cargos and high weight factor load stresses. To strengthen this type of floor, various devices and means have been attempted such as described in U.S. Patent No. 3,416,280 to Young, U.S. Pat. No. 3,128,851 to Deridder et al., and U.S. Patent 4,091,743 to Lemon. However, none of these overcomes the disadvantages of being more complex and expensive to manufacture than the simple T-shape or the U-shaped duct floor.
A disclosure to combine T-shapes and U-shapes into individual floor panels is made in U.S. Pat. No. 4,631,891 to Donavich. This patent discloses a floor structure made up of panels that have both T-shapes and U-shapes extruded onto each individual panel. The patent discloses several different combinations of T-shapes and U-shapes on different panels.
Although this combination on individual panels could provide floors on which heavy cargo can be placed with good air circulation, there still exists the possibility of damage by forklift trucks which inadvertently tread onto the T-shaped elements. Such floors do not define definite areas upon which mechanical lift trucks can mount without the possibility of damaging T-shaped elements.
U.S. Pat. No. 2,753,018 to Curell discloses a panel assembly arrangement for floor structures. This patent disclosure proposes the use of two outer J-panels, a U-shaped center panel and a plurality of intermediate extruded metal panels.
Despite the foregoing disclosures there has existed a need for an integrated floor structure which can withstand the severe stresses of forklifts and other mechanical loading devices that are used in cargo transport and loading, but which still provides significant air circulation beneath the cargo. Thus, there is a need for a floor structure that defines aisles upon which heavy mechanical loaders may consistently bear down without the fear of crushing weaker, but greater air circulating, areas of the floor.